A heald frame consists of frame staves forming upper and lower frameworks and side stays forming left and right frameworks and is provided with a number of healds, each heald having a warp accepted therethrough. The heald frame, as required for upward and downward reciprocating motion, is coupled at the lower or upper end to connecting rods of a shedding mechanism. The shedding mechanism comprises cam assemblies and crank assemblies and its movement is transmitted via the connecting rods to the heald frame which in turn travels upward and downward.
The selection of a heald frame corresponds to the type of weaving needed. A change of weaving thus involves the replacement of a heald frame, causing frequent attaching and detaching of couplers between the heald frame and the connecting rod. Also, each coupler is located inward in a loom, offering only a small space for attaching and detaching of the same. To make matters worse, a known coupler is rather awkward in the application of attachment and may cause loose lockup at the joint.